The bonding pads that are adapted for soldering common electronic components, such as capacitors, resistors, inductors, or LEDs, are usually designed to be larger than the solder pin areas of those electronic components. During the soldering of foregoing electronic components to their corresponding bonding pad on a printed circuit board by passing the printed circuit board in a soldering pot, the electronic components to be soldered are still free to move around since the solder paste is still in liquid form, so that after passing through the soldering pot and the electronic components are soldered, some of the electronic components can be displaced and thus have contact to other electronic components that are short circuited. For LEDs, any displacement to the soldering of the LEDs may cause the LEDs to interfere with each other during assembling of a backlight module, so that some of the LEDs may be forced to come off the backlight module, and some may not be aligned to the light entrance of their corresponding light guide panel, and thus the brightness of the backlight module is declined.
Generally, any one bonding pad configured on a printed circuit board is specifically designed for the electronic components of a single specification. However, it is noted that the electronic components, such as capacitors, resistors and inductors, are usually constructed with various specifications. For instance, the size of an electronic component in 0402 specification is about 0.4 mm×0.2 mm, and the size of an electronic component in 0603 specification is about 0.6 mm×0.3 mm, so that the bonding pads designed respectively for the electronic components in 0402 specification and in 0603 specification should be formed according to different specifications. Therefore, unless a manufacture is constantly maintained a great inventory for the electronic components of a specific specification, it is more than often for the manufacturer to suffer a short stock problem when the suppliers are not able to supply sufficient its required electronic components of the specific specification, or the date of deliver is delayed. Nevertheless, if the manufacturer is propelled to replace the electronic components of the specific specification with electronic components of other specification, its circuit board design must be changed, and that is going to cause the cost of manufacture to increase, or even cause the delay in product delivery.
There are already many studies for solving the aforesaid problem. One of which is a bonding pad for printed circuit board, disclosed in TW Pat. No. I271135, that is provided for a first surface mounting device and a second surface mounting device to mount thereon. The bonding pad includes a plurality of pads that each of the pads is composed of a first part and a second part, whereas the first part is shaped about the same as the pin area of the first surface mounting device so as to be provided for the first surface mounting device to mount thereon, while the second part is shaped about the same as the pin area of the second surface mounting device so as to be provided for the second surface mounting device to mount thereon. Thus, the aforesaid bonding pad can be used for mounting different surface mounting devices without exhausting much of the limited layout space available on the printed circuit board. However, as each pad in the bonding pad is composed of a first part and a second part that are connected with each other and form a comparatively large solder area, device displacement or tombstoning might be caused when it is used for soldering a small-sized second surface mounting device.
Another such study is a highly compatible solder pad structure, disclosed in TW Pat. No. I256698, which is adapted for soldering electronic components of various specifications by the application of surface mounted technology, by that an electronic component to be mounted is able to maintain good electrical connection to at least two solder pads on a circuit board. The aforesaid solder pad structure is featuring in that: there are recesses formed on the two neighboring solder pads on a circuit board respectively at sides neighboring to each other and at positions corresponding to each other, so that electronic components of different specifications can be soldered onto the two solder pads at areas defined by the two recesses. Accordingly, by the arrangement of the recesses, the solder pad structure can be provided for electronic components of different specifications to mount thereon that not only the manufacturing cost can be reduced, but also the aforesaid tombstoning can be resolved. However, since each of the solder pad in the solder pad structure is shaped like a bar, there can be two third of the solder pad structure that is not occupied when it is used for soldering a small-sized electronic component, so that many of the limited layout space available on the circuit board is wasted. In addition, the aforesaid solder pad structure can only be adapted for only the electronic components of 0201 and 0204 specifications, that when it is used for soldering other electronic components whose sizes are smaller than the 0201 specification, device displacement and tombstoning are still inevitable.